Method for manufacturing a light emitting diode having a transparent substrate

ABSTRACT

A light emitting diode having a transparent substrate and a method for manufacturing the same. The light emitting diode is formed by creating two semiconductor multilayers and bonding them. The first semiconductor multilayer is formed on a non-transparent substrate. The second semiconductor multilayer is created by forming an amorphous interface layer on a transparent substrate. The two semiconductor multilayers are bonded and the non-transparent substrate is removed, leaving a semiconductor multilayer with a transparent substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 09/683,959filed Mar. 6, 2002, now U.S. Pat. No. 6,867,426.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a light emitting diode, morespecifically to a light emitting diode having a transparent substrate,and a method for manufacturing the same.

2. Description of the Prior Art

Light emitting diodes (LEDs) are employed in a wide variety ofapplications including optical display devices, traffic lights, datastorage equipment, communication devices, illumination apparatuses, andmedical treatment equipment. Some of the main goals of engineers whodesign LEDs are to increase the brightness of the light emitted fromLEDs and to reduce the cost of manufacturing LEDs.

U.S. Pat. No. 5,783,477 discloses a method of bonding two compoundsemiconductor surfaces to produce an ohmic contact interface. The methodof manufacturing a prior art LED is to create an ohmic contact interfaceby aligning the crystallographic orientation and rotational alignment oftwo semiconductor surfaces and applying uniaxial pressure to thesemiconductor wafers at a temperature of 1000° C. In actual procedure,however, it is difficult and expensive to align the crystallographicorientation and rotational alignment of the two semiconductor surfaces.

SUMMARY OF INVENTION

It is an objective of the claimed invention to provide a light emittingdiode (LED) having a transparent substrate and the method formanufacturing the same. The method involves wafer bonding a transparentsubstrate with a compound semiconductor multilayer. The compoundsemiconductor multilayer comprising the LED is grown on anon-transparent substrate. The transparent substrate and the compoundsemiconductor multilayer are bonded using an amorphous interface layer.After the bonding, the non-transparent substrate is removed, leaving anLED with a transparent substrate. The method according to the claimedinvention will simplify the procedure of manufacturing LEDs, therebyreducing costs. The method also solves the problem of aligning thecrystallographic orientation and rotational alignment of the twosemiconductor surfaces and creates a light emitting diode with anincreased luminance.

In the claimed invention, a light emitting diode comprises a sapphiretransparent substrate. Formed above the substrate is an indium tin oxide(ITO), a top surface of which comprises a first surface region and asecond surface region. On the first surface region, the layers of thesemi-conductor multilayer stacked from bottom to top are: A p⁺-typecontact layer of GaAs, a p-type cladding layer of AlGaInP, a multiplequantum well (MQW) light-emitting layer, an n-type cladding layer ofAlGaInP, an n-type stop layer of AlGaAs, and an ITO transparentconductive layer. A first electrode is located on the ITO transparentconductive layer, and a second electrode is located on the secondsurface region.

The claimed invention also details a method for manufacturing the lightemitting diode. The first step is to form a first multilayer on ann-type GaAs semiconductor substrate. An n-type stop layer of AlGaAs isformed on the semiconductor substrate. An n-type cladding layer ofAlGaInP is formed on the n-type stop layer. An MQW light-emitting layerof AlGaInP is formed on the n-type cladding layer. A p-type claddinglayer of AlGaInP is formed on the MQW light-emitting layer. A p³⁰ -typecontact layer of GaAs is formed on the p-type cladding layer. A secondmultilayer is formed on a sapphire substrate. An amorphous interfacelayer of ITO is formed on the sapphire substrate. A third multilayer isproduced by placing the first multilayer on the second multilayer andbonding the first multilayer to the second multilayer by elevatingtemperature. Next, the n-type GaAs semiconductor substrate of the newlycreated third multilayer is removed, and an ITO transparent conductivelayer is formed on the stop layer to produce a fourth multilayer. Next,an exposed interface region is formed by etching away a portion of thefourth multilayer from the ITO transparent conductive layer to the ITOamorphous interface layer. Finally, a first contact electrode and asecond contact electrode are formed on the ITO transparent conductivelayer and the exposed interface region, respectively.

These and other objectives of the claimed invention will no doubt becomeobvious to those of ordinary skill in the art after having read thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view of a high brightness light emittingdiode having a transparent substrate according to the first embodimentof the present invention.

FIG. 2 is a cross sectional view showing a first semiconductormultilayer before wafer bonding during the manufacturing methodaccording to the present invention.

FIG. 3 is a cross sectional view showing an amorphous interface layerand a second semiconductor multilayer before wafer bonding during themanufacturing method according the present invention.

FIG. 4 is a cross sectional view showing a third semiconductormultilayer after wafer bonding, but before removal of thenon-transparent substrate during the manufacturing method according thepresent invention.

FIG. 5 is a cross sectional view showing a third semiconductormultilayer after removal of the non-transparent substrate and formationof an ITO transparent conductive layer during the manufacturing methodaccording the present invention.

FIG. 6 is a cross sectional view of a high brightness light emittingdiode having a transparent substrate according to the second embodimentof the invention.

FIG. 7 is a cross sectional view of a high brightness light emittingdiode having a transparent substrate according to the third embodimentof the invention.

FIG. 8 is a cross sectional view of a high brightness light emittingdiode having a transparent substrate according to the fourth embodimentof the invention.

DETAILED DESCRIPTION

FIG. 1 is a cross sectional view of a high brightness light emittingdiode (LED) 1 having a transparent substrate according to the firstembodiment of the present invention. In the LED 1, an indium tin oxide(ITO) amorphous interface layer 11 is formed on a sapphire transparentsubstrate 10. A top surface of the ITO amorphous interface layer 11comprises a first surface region and a second surface region. The LEDfurther comprises layers stacked upon each other on the first surfaceregion in the following order, bottom to top: a contact layer of p⁺-typeGaAs 12, a cladding layer of a p-type AlGaInP 13, a multiple quantumwell (MQW) light-emitting layer 14, a cladding layer of n-type AlGaInP15, a stop layer of n-type AlGaAs 16, and an ITO transparent conductivelayer 18. A first electrode 19 is located on the ITO transparentconductive layer 18, and a second electrode 20 is located on the secondsurface region.

FIG. 2 and FIG. 3 illustrate a method for manufacturing the lightemitting diode 1 according to the first embodiment of the presentinvention. A first semiconductor multilayer 2 is created by firstforming an n-type stop layer 16 of AlGaAs on an n-type GaAssemiconductor substrate 17. Then an n-type cladding layer 15 of AlGaInPis formed on the n-type stop layer 16. An MQW light-emitting layer 14 ofAlGaInP is formed on the n-type cladding layer 15. A p-type claddinglayer 13 of AlGaInP is formed on the MQW light-emitting layer 14, and ap⁺-type contact layer 12 of GaAs is formed on the p-type cladding layer13. Next, a second semiconductor multilayer 3 is created. The secondsemiconductor multilayer 3 comprises an amorphous interface layer 11 ofITO formed on a sapphire substrate 10. As is shown in FIG. 4, a thirdsemiconductor multilayer 4 is produced by inverting the firstsemiconductor multilayer 2, placing it on the semiconductor multilayer3, and bonding the first semiconductor multilayer 2 to the secondsemiconductor multilayer 3 by elevating temperature and applyinguniaxial pressure to the semiconductor multilayers. FIG. 4 and FIG. 5show the next step, which comprises the removal of the n-type GaAssemiconductor substrate 17 from the multilayer 4 and the formation of afirst ITO transparent conductive layer 18 on the n-type stop layer 16,producing a fourth semiconductor multilayer 5. Next, an interfaceexposed region is formed by etching away a portion of the fourthsemiconductor multilayer 5 from the first ITO transparent conductivelayer 18 to the ITO amorphous interface layer 11. Finally, a firstcontact electrode 19 and a second contact electrode 20 are formed on thefirst ITO transparent conductive layer 18 and the interface exposedregion, respectively.

FIG. 6 illustrates a light emitting diode 6 having a transparentsubstrate according to a second preferred embodiment of the presentinvention. A transparent substrate 611 of p-type GaP is formed on anohmic contact electrode 610. A first p-type contact layer 612 of GaAs isformed on the transparent substrate 611. An indium tin oxide (ITO)amorphous interface layer 613 is formed on the first p⁺-type contactlayer 612. A second p⁺-type contact layer 614 of GaAs is formed on theITO amorphous interface layer 613. A p-type cladding layer 615 ofAlGaInP is formed on the second p⁺-type contact layer 614. A multiplequantum well (MQW) light-emitting layer 616 of AlGaInP is formed on thep-type cladding layer 615. An n-type cladding layer 617 of AlGaInP isformed on the MQW light-emitting layer 616. An n-type stop layer 618 ofAlGaAs is formed on the n-type cladding layer 617. An ITO transparentconductive layer 619 is formed on the n-type stop layer 618. Anelectrode 620 is formed on the ITO transparent conductive layer 619.

FIG. 7 illustrates a light emitting diode 7 having a transparentsubstrate according to a third preferred embodiment of the presentinvention. A transparent substrate 711 of n-type GaP is formed on afirst electrode 710. An indium tin oxide (ITO) amorphous interface layer713 is formed on the transparent substrate 711. An n-type contact layer714 of GaP is formed on the ITO amorphous interface layer 713. An n-typecladding layer 715 of AlGaInP is formed on the n-type contact layer 714.A multiple quantum well (MQW) light-emitting layer 716 of AlGaInP isformed on the n-type cladding layer 715. A p-type cladding layer 717 ofAlGaInP is formed on the MQW light-emitting layer 716. A p-type bufferlayer 718 of AlGaAs is formed on the p-type cladding layer 717. Ap⁺-type contact layer 719 of GaAs is formed on the p-type buffer layer.An ITO transparent conductive layer 720 is formed on the p⁺-type contactlayer 719. A second electrode 721 is formed on the ITO transparentconductive layer 720.

FIG. 8 illustrates a light emitting diode 8 having a transparentsubstrate according to a fourth preferred embodiment of the presentinvention. An indium tin oxide (ITO) amorphous interface layer 811 isformed on a transparent substrate 810 of glass. A top surface of the ITOamorphous interface layer 811 comprises a first surface region and asecond surface region. An n⁺-type reverse tunneling contact layer 814 ofInGaN is formed on the first surface region. A p-type cladding layer 815of GaN is formed on the n⁺-type reverse tunneling contact layer 814. Amultiple quantum well (MQW) light-emitting layer 816 of InGaN is formedon the p-type cladding layer 815. An n-type cladding layer 817 of GaN isformed on the MQW light-emitting layer 816. A first Ti—Al contactelectrode is formed on the n-type cladding layer 817. A second electrode820 is formed on the second surface region.

According to the description of these embodiments, LEDs having atransparent substrate can be manufactured by a method of bonding twochips using an amorphous interface layer. LEDs made according to thepresent invention are easier to manufacture, less expensive tomanufacture, and brighter than those made according to the prior art.

While the invention has been disclosed and described with reference tothese preferred embodiments, the scope of the invention is not limitedto these preferred embodiments. Any variation and modifications of theinvention still falls within the spirit and scope of the invention. Forexample, using a transparent conductive layer of adhesive agent insteadof a single-crystal interface layer or using a single quantum welllight-emitting layer instead of a multiple quantum well light-emittinglayer cannot escape the scope and spirit of the invention. Moreover, themanufacturing method of the present invention is also suitable formanufacturing a light emitting diode having a non-transparent substrate.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device may be made while retainingthe teachings of the invention. Accordingly, the above disclosure shouldbe construed as limited only by the metes and bounds of the appendedclaims.

1. A method for manufacturing a light emitting diode having atransparent substrate, the method comprising: forming a semiconductormultilayer on a first substrate producing a first multilayer structure;forming a conductive amorphous interface layer on a second substrate,the second substrate being transparent in nature, producing a secondmultilayer structure; bonding the first multilayer structure to thesecond multilayer structure, producing a third multilayer structure; andremoving the first substrate from the third multilayer structure.
 2. Themethod of claim 1 further comprising a step of forming a transparentconductive layer on the third multilayer structure after removing thefirst substrate.
 3. The method of claim 1, wherein the amorphousinterface layer is made of at least one selected from a group consistingof indium tin oxide, indium cadmium oxide, antimony tin oxide; andtransparent adhesive agent.
 4. A method for manufacturing a lightemitting diode, comprising: forming a semiconductor multilayer on afirst substrate producing a first multilayer structure; forming aconductive amorphous interface layer on a second substrate, the secondsubstrate being transparent in nature, producing a second multilayerstructure; bonding the first multilayer structure to the secondmultilayer structure, producing a third multilayer structure; andremoving the first substrate from the third multilayer structure.
 5. Themethod of claim 4 further comprising a step of forming a transparentconductive layer on the third multilayer structure after removing thefirst substrate.
 6. The method of claim 4, wherein the amorphousinterface layer is made of at least one selected from a group consistingof indium tin oxide, cadmium tin oxide, antimony tin oxide, andtransparent adhesive agent.
 7. The method of claim 1 further comprisingetching away a portion of the first multilayer structure to partiallyexpose the amorphous interface layer.